A novel bone registration method using impression molding and structured-light 3D scanning technology.

Accurate bone registration is critical for computer navigation and robotic surgery. Existing registration systems are expensive, cumbersome, limited in accuracy and/or require intraoperative radiation. We recently reported a novel method of registration utilizing an inexpensive, compact, and X-ray-free structured-light 3D scanner. However, this technique is not always practical in a real surgical setting where soft tissue and blood can obstruct the continuous line-of-sight required for structured-light technology. We sought to remedy these limitations using a novel technique using rapid-setting impression molding to capture bone surface features and scan the undersurface of the mold with a structured-light scanner. The photonegative of this mold is compared to the preoperative computed tomography (CT)-scan to register the bone. A registration accuracy study was conducted on 36 CT-scanned femur sawbones, simulating typical exposure in hip/knee arthroplasty and bone tumor surgery. A cadaver experiment was also conducted to evaluate the feasibility of using the impression molding in a more realistic operating room setting. The registration accuracy of the proposed technique was 0.50 ± 0.19 mm. This was close to the reported accuracy of 0.43 ± 0.18 mm using a structured-light scanner without impression molding (p = 0.085). In comparison, historical values for "paired-point" and intraoperative CT image-based registration methods currently used in modern robotic/computer-navigation systems were 0.68 ± 0.14 mm (p = 0.004) and 0.86 ± 0.38 mm, respectively. The registration accuracy of the cadaver experiment was consistent with that of sawbone experiments. Although future studies are needed to extend to human subjects, this study shows that the impression molding method can produce comparable or better registration accuracy than the existing techniques.

Cadmium uptake reduction in paddy rice with a combination of water management, soil application of calcium magnesium phosphate and foliar spraying of Si/Se.

A field experiment with 24 different treatments was carried out to study the effects of a combination of water management (WM), soil application of calcium magnesium phosphate (CMP), and foliar spraying of Si/Se on Cd uptake by paddy rice (Teyou 524). The water management modes included W1 (conventional water management) and W2 (flooding during the whole growth period). The application of CMP included P1 (1800 kg·hm-2) and P2 (3000 kg·hm-2). The leaf spraying regulations included LS (2.0 mmol·L-1 Na2SiO3), LX (25 µmol·L-1 Na2SeO3), and LSX (1.0 mmol·L-1 Na2SiO3 and 12.5 µmol·L-1 Na2SeO3). The results indicated that, compared to the control (W1), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W2, P1, P2, W2P1 and W2P2, respectively; but the grain yield was reduced under W2 condition. Some individual treatments, including W2, P1, P2, LS, LX, and LSX, could reduce Cd concentration in the grain by 23.1-60.3%; but the combined regulations could reduce grain Cd concentrations up to 79.5%. Only the combined mode of CMP and leaf spraying of Si/Se could control grain Cd concentration below the Chinese National Food Safety Standard (0.2 mg·kg-1). Combined modes of fertilizer application (W2 and CMP) and foliar spraying (Si/Se), including W2P2LS, W2P2LX, W2P2LSX, were the most effective in reducing the Cd transport coefficients of both root-to-straw (RS) and straw-to-seed (SS). Considering Cd concentration in grain, treatments W2P2LS and W2P2LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg-1 and 0.089 mg·kg-1 in grain, respectively. These results demonstrated that combined manipulation of the root zone (W2 and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.

Remediation mechanisms of mercapto-grafted palygorskite for cadmium pollutant in paddy soil.

The immobilization agent was the key factor that determined the success of remediation of heavy metal polluted soil. In this study, mercapto-grafted palygorskite (MP) as a novel and efficient immobilization agent was utilized for the remediation of Cd-polluted paddy soil in pot trials, and the remediation mechanisms were investigated in the aspect of soil chemistry and plant physiology with different rice cultivars as model plants. Mercapto-grafted palygorskite at applied doses of 0.1-0.3% could reduce Cd contents of brown rice and straws of different cultivars significantly. Both reduced DTPA-extractable Cd contents in rhizosphere and non-rhizosphere soil and decreasing Cd contents in iron plaques on rice root surfaces confirmed that MP was an efficient immobilization agent for Cd pollutant in paddy soil. In the aspect of soil chemistry, the pH values of rhizosphere and non-rhizosphere soils had no statistical changes in the MP treatment groups, but their zeta potentials decreased obviously, indicating that MP could enhance the fixation or sorption of Cd on soil compositions. In the aspect of antioxidant system, MP could increase POD activity of rice roots significantly to alleviate the stress of Cd to roots, and resulted in the decrease of T-AOC, SOD, and CAT activities of rice roots of the selected cultivars. MP had no inhabitation or enhancement effects on TSH of rice roots but enhance the contents of MTs and NPT to binding Cd to complete detoxification process. MP as a novel and efficient immobilization agent could complete the remediation effects through soil chemistry and plant physiological mechanisms.

Dietary exposure estimates of 16 polycyclic aromatic hydrocarbons (PAHs) in Xuanwei and Fuyuan, counties in a high lung cancer incidence area in China.

Xuanwei and Fuyuan are located in the southwest of China and have the highest lung cancer incidence in China, possibly even highest in the world. Dietary samples were collected from these two counties and the contamination status of sixteen polycyclic aromatic hydrocarbons (PAHs) were determined. PAH components, food constituents, dietary exposure level, as well as spatial difference, were studied in the different groups. The percentage of dietary intake to total intake of PAHs was calculated and the relationship between the dietary intake of PAHs and the abnormal lung cancer incidence was primarily discussed. The results showed that rice and potatoes were the main foods of the local residents in Xuanwei and Fuyuan. The daily exposure doses of Bap (benzo[a]pyrene), total PAHs, and TEQs (toxic equivalents) based on Bap toxicity in two counties were estimated to be 458 ng d(-1), 14,532 ng d(-1), and 896 ng d(-1), respectively, which were much less than those in other cities reported previously. The lower ingestion amount of food with a relatively higher content of PAHs, such as meat and fish, could account for the lower exposure doses. PAHs with less than 4 rings occupied a high percentage of the total PAHs in food samples. The exposure doses varied significantly among different sites and even different families at the same site. Dietary exposure was not the main exposure route of PAHs at most sites. It appears that there was not a direct relationship between dietary exposure and the lung cancer incidence. However, high ratios of dietary intake to total PAHs intake (1.33%-70.61%) were found in several areas and rational diet suggestions should be given in these areas in the future.

Assessment of 20 organochlorine pesticides (OCPs) pollution in suburban soil in Tianjin, China.

Soil contamination with organochlorine pesticides has aroused worldwide concerns considering their high toxicities and long-term persistence. In this study, 87 representative soil samples from suburban areas (Xiqing, Dongli, Jinnan, Beichen) of Tianjin, the third biggest city in China, were collected to evaluate the pollution of 20 organochlorine pesticides. Surface soil samples were air-dried and sieved. Ultrasonic extraction was used for organochlorine pesticides preparation prior to analysis with gas chromatography-mass spectrometry. It was revealed that p,p'-DDE, p,p'-DDD, o,p'-DDT, o,p'-DDD, hexachlorobenzene, dicofol and beta-HCH were seven pesticides detected most frequently. DDTs, HCHs and hexachlorobenzene were the predominant pesticide pollutants in soil. Spatial variation of these organochlorine pesticides in soil was illustrated; Pollution levels, characteristics and possible sources were also investigated. Most of other 13 kinds of pesticides were detected and the frequencies of detection were calculated to reveal the pollution status, which ranged from 0.0% (aldrin, dieldrin and endrin) to 34.5% (p,p'-DDT). These data were helpful to figure out the pollution of organochlorine pesticides and could be further used to evaluate the health risk associated with soil pollution.